The present invention relates to a technique for connecting a slider pad and a lead pad of a head gimbal assembly included in a magnetic disk drive. More particularly, the present invention relates to a technique for making a soldered connection between the slider pad and the lead pad by re-irradiating a solder mass with a laser beam, the solder mass being deposited on the slider pad as a result of a solder ball being irradiated with the laser beam.
In the magnetic disk drive, a head formed in a slider (a structure integrating a head with a slider will hereinafter be referred to as a head/slider) flies above a surface of a magnetic disk with an extremely small gap from the surface and reads data from, or writes data to, the magnetic disk. The head/slider includes an air bearing surface (hereinafter referred to as ABS) formed on a surface thereof facing the magnetic disk. The ABS is structured such that positive pressure acting on the slider as a lifting force is produced when an air stream produced on the surface of a spinning magnetic disk flows past a space between the ABS and the surface of the magnetic disk. The ABS is also structured so as to produce negative pressure at other times for stabilizing attitudes during flying.
The head/slider is mounted on a spring structural body called flexure. While the head/slider flies above the surface of the magnetic disk, the flexure makes pivotal movement or gimbal movement so that the gap between the head and a magnetic layer of the disk may fall within a predetermined range. The flexure is mounted on a load beam which, in turn, is supported by an actuator assembly driven by a voice coil motor (hereinafter referred to as VCM). A structure having the head/slider, the flexure, a lead, and the load beam as main components thereof is called a head gimbal assembly (hereinafter referred to as HGA). The magnetic disk drive commonly includes a circuit board mounted with circuit devices for controlling data communications and the magnetic disk drive. Electric connection is made between the circuit board and the head using the lead. The head is embedded in the slider main body and connected to a slider pad formed on an end face of the head/slider. The slider pad is connected to a lead pad formed on an end portion of the lead using solder.
Examples of methods of connecting the slider pad to the lead pad using solder include a solder ball connection technique. The solder ball connection technique is superior as a soldering connection technique applicable to micromini sliders, since a soldered connection can be made with no mechanical stress applied to the slider pad or lead pad. FIG. 14 includes views for illustrating a condition in which the lead pad and the slider pad are connected together using the solder ball connection technique. FIG. 14(A) shows metal layers 319a, 319b, dielectric layers 317a, 317b, and a lead 321. The metal layers 319a, 319b constitute a flexure support structure. The dielectric layers 317a, 317b made of polyimide are stacked on the metal layers 319a, 319b, respectively. The lead 321 is formed by stacking a copper layer on top of the dielectric layer 317b. A head/slider 311 is mounted on the dielectric layer 317a with an ABS 323 opposing the magnetic disk facing up. A magnetic head is embedded internally in the head/slider 311 so as to achieve magnetic coupling between the magnetic head and the magnetic disk opposing the ABS 323. In addition, a slider pad 313 for connecting the magnetic head and the lead 321 is formed on a side surface on an end portion of the head/slider 311.
The metal layer 319a for supporting the head/slider 311 is called a flexure tongue. The flexure tongue makes gimbal movement or pivotal movement about a dimple formed in the load beam (not shown) as a pivot when the head/slider 311 flies above the magnetic disk surface. The lead 321 extends, in front of the slider pad 313, to a position to define a space 325 between the head/slider 311 and the lead 321. A lead pad 329 is formed at a leading end portion of the lead 321.
The solder ball connection technique typically follows these steps. Specifically, a solder ball 315 is temporarily deposited so as to come in contact with both the slider pad 313 and the lead pad 329. The solder ball 315 is then irradiated with a laser beam emitted from the direction of an arrow A and is thus melted. The laser beam is then shut down so that the melted solder cools down. A solder fillet 327 shown in FIG. 14(B) is thereby formed to make electric connection between the slider pad 313 and the lead pad 329. The solder ball connection technique is, however, associated with problems of improper connection unique thereto. Possible problems include: the molten solder attracted one-sidedly to either one of the pads during reflow of the solder ball 315 using laser energy, causing the solder fillet 327 to be connected only to one of the pads; an insufficient area of connection between the solder fillet 327 and the pads; a lack of sufficient connection strength; and a pad short-circuited with an adjacent one.
Patent Document 1 (Japanese Patent Laid-open No. 7-106739) discloses a technique that proceeds as below. Specifically, a mounting board is heated by a heater to a temperature level below a melting point of solder, thereby reducing peel strength of the solder ball relative to flux; an adhesion layer of an adsorption device is rollingly transferred onto the mounting board, thereby peeling the solder ball from the mounting board through adhesion. Patent Document 2 (Japanese Patent Laid-open No. 1-130590) discloses a technique, in which flux is softened by heated steam and the flux and a solder ball are removed by a blowing force. Patent Document 3 (Japanese Patent Laid-open No. 11-26918) discloses a technique in which solder is heated to a temperature at which the solder softens, and the solder is grounded off with a grinder.